Hydrodynamics of bubble flow through a porous medium with applications to packed bed reactors

TL;DR

This paper investigates bubble flow dynamics in packed bed reactors under various gravity conditions using simulations, revealing key pore-scale mechanisms and introducing new dimensionless numbers to predict bubble behavior.

Contribution

It introduces a novel simulation approach and dynamic scales to analyze bubble flow, highlighting the effects of gravity and flow forces in packed bed reactors.

Findings

Different pore-scale mechanisms identified, such as capillary and buoyancy entrapment.

New Weber-like dimensionless numbers delineate bubble entrapment from displacement.

Gravity significantly influences bubble flow regimes in packed beds.

Abstract

Gas-liquid flows through packed bed reactors (PBRs) are challenging to predict due to the tortuous flow paths that fluid interfaces must traverse. Experiments at the International Space Station showed that bubble and pulse flows are predominately observed under microgravity conditions, while the trickle and spray flows observed under terrestrial conditions are not present in microgravity. To understand the physics behind the former experiments, we simulate bubble flow through a PBR for different packing-particle-diameter-based Weber numbers and under different gravity conditions. We demonstrate different pore-scale mechanisms, such as capillary entrapment, buoyancy entrapment, and inertia-induced bubble displacement. Then, we perform a quantitative analysis by introducing new dynamic scales, dependent upon the evolving gas-liquid interfacial area, to understand the dynamic trade-offs between the inertia, capillary, and buoyancy forces on a bubble passing through a PBR. This analysis leads us to define new dimensionless Weber-like numbers that delineate bubble entrapment from bubble displacement.